Overview

Lead frame chemical etching forms lead frames by dissolving metal instead of cutting it: a photoresist mask is laminated to both sides of the strip, the lead pattern is exposed and developed, and the unprotected copper or alloy 42 dissolves in a matched etchant until the leads, tie bars and mounting holes are released. Because no punch ever touches the stock, the leads stay flat and free of roll-over burr, which matters once the pitch drops below 0.5 mm and any whisker of metal can bridge two pins. Strips run from 0.05 mm to 0.5 mm thick in oxygen-free copper C1100, copper-iron C194, alloy 42 (Fe-42Ni), phosphor bronze and beryllium copper.

Designers choose lead frame chemical etching for three reasons. Fine-pitch leads and 0.15 mm webs hold without the stretch and twist that stamping leaves on thin stock. Half-etch features — dimples, recessed tie bars, bond-pad windows and alignment marks — are produced in the same pass at controlled depth, usually 30–50% of the strip thickness. And a new part number only needs new artwork, so prototype frames and revision loops carry no die work. The result is a frame that plates cleanly, indexes reliably in the die-bond machine and matches the approved sample from the first reel to the last.

Parameter Window

• Available Materials: oxygen-free copper C1100, copper-iron C194, alloy 42 (Fe-42Ni), phosphor bronze, beryllium copper
• Material Thickness Range: 0.05–0.5 mm
• Tolerance: ±0.02 mm on lead width and pitch, ±0.05 mm on outline, ±0.01 mm on half-etch depth
• Minimum Feature: 0.1 mm lead width and 0.15 mm lead gap on 0.15 mm stock
• Surface Options: matte tin, silver, Ni/Pd/Au pre-plated strip, selective plating, deburring, forming
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork Review — Convert Gerber or DXF data to etch artwork and check lead width, pitch and tie-bar layout against strip thickness.
2. Material Selection — Match alloy and temper to the package: copper for conductivity and wire bonding, alloy 42 for glass-to-metal sealing.
3. Cleaning & Lamination — Degrease both sides and laminate dry-film resist under heat and pressure so no bubbles sit between fine leads.
4. UV Exposure — Expose both sides through registered film so top and bottom patterns align within ±0.02 mm.
5. Development — Wash out unexposed resist to open lead, hole and half-etch areas, then inspect for pinholes over the webs.
6. Etching — Spray etchant from both sides with controlled temperature and line speed until leads are released and half-etch features reach target depth.
7. Stripping & Plating — Remove resist, neutralize, deburr and apply the specified finish: matte tin, silver, Ni/Pd/Au or selective plating on bond areas.
8. Inspection & Packaging — Measure lead width, pitch and half-etch depth on a vision system, then pack frames in trays or tape with a first-article report.

Core Advantages

1. Burr-free leads: Chemical release leaves no roll-over or whisker, so adjacent pins cannot bridge at fine pitch.
2. No stamping stress: Leads are not pulled through a die, so frames stay flat and free of work hardening at the bend zones.
3. Half-etch in one pass: Dimples, recessed tie bars and bond-pad windows reach the same controlled depth across the panel.
4. Fine-pitch capability: 0.4 mm pitch with 0.15 mm webs runs stably on 0.1–0.15 mm copper strip.
5. Fast revision loops: A new film replaces a new die, so design changes reach assembled samples in days instead of weeks.
6. Plating-ready surface: Clean, oxide-free copper accepts matte tin, silver and Ni/Pd/Au uniformly across the strip, and lead frame chemical etching keeps the first and the ten-thousandth frame identical.

Typical Applications

• Fine-pitch IC packages: QFP and SOP style frames with 0.4–0.65 mm pitch leads etched from 0.15 mm copper strip.
• Power device frames: Wide-lead frames for transistors and modules where current bars and screw holes are etched together.
• LED lamp frames: Reflector cups and lead fingers half-etched into the same strip before plating.
• Sensor and MEMS carriers: Alloy 42 frames sealed to glass or ceramic for pressure and optical sensors.
• Relay and switch frames: Armature and contact frames with flatness requirements well below stamped equivalents.
• Connector and terminal frames: Multi-pin terminal strips where burr-free edges protect thin insulator housings.

Design Notes & Process Considerations

1. Web width versus thickness: Keep the narrowest lead at or above 1× material thickness to limit undercut and keep sidewalls vertical.
2. Pitch and tie bars: State the required pitch, tie-bar width and whether tie bars are etched away or removed later on the assembly line.
3. Half-etch callout: Give the depth for dimples and recessed windows — typically 30–50% of strip thickness — together with the datum they are measured from.
4. Flatness and burr: Call out flatness per 100 mm and burr-free edges so frames index cleanly in the die-bond fixture.
5. Plating and packaging: Specify plating type, thickness and whether frames are supplied in trays or on tape with protective film.
6. Panel layout: Nest frames on shared rails with common registration holes to cut handling cost and keep pitch accuracy across the panel.